Signal processing arrangements typically comprise various functional entities for carrying out various types of operations. There is an ongoing trend to implement these functional entities by means of digital circuits rather than analog circuits, although analog circuits remain indispensable. There is also an ongoing trend to implement more and more functional entities on a single integrated circuit.
There is thus a need for combining analog circuits and digital circuits on a single integrated circuit. An integrated circuit that comprises digital circuits may be taken as a basis to which one or more analog circuits should be added. In a manner of speaking, analog circuits should adapt to integrated circuit manufacturing processes for digital circuits. Since digital circuits are typically manufactured in CMOS technology, there is a need for high-performance analog circuits that can be manufactured in CMOS technology (CMOS is an acronym for complementary metal-oxide semiconductor).
Numerous signal processing arrangements require an amplifier for amplifying analog signals. For example, in an integrated receiver system, a radiofrequency signal is typically amplified before digitizing this signal, or a frequency-converted version thereof. In such an integrated receiver system, functional entities such as, for example, filters, demodulators, and decoders, may be implemented by means of digital circuits. The digital circuits process a digital version of the radiofrequency signal obtained by digitization. This digital processing can be relatively precise. Receiver performance will substantially depend on analog signal processing, prior to the digitization, which involves amplification. For example, the amplifier should exhibit a sufficiently high degree of linearity so that distortion requirements are met.
An interesting amplifier topology, which can be manufactured in CMOS technology, is based on complementary transistors of opposite conductivity type, which are arranged in series between two supply lines. This amplifier topology is interesting because of its inherent structural simplicity, relatively low power consumption, and relatively high power gain. Moreover, this amplifier topology exhibits a relatively linear transfer function.
U.S. Pat. No. 3,914,702 describes a complementary field effect transistor amplifier, which is biased to a given operating point. To that end, a reference potential is applied to its input terminal. The operating potentials supplied to the amplifier are varied in accordance with its output signal. At least one other complementary field effect amplifier, which is integrated upon a common substrate with the first amplifier, receives operating potentials that also vary in accordance with the output signal of the first amplifier. This is done to maintain the quiescent operating point of the other amplifier at a value substantially equal to the given operating point of the first amplifier. The aforementioned patent dissuades use of a feedback resistor.